Methods for ablation with radiant energy

ABSTRACT

A method of treating atrial fibrillation includes the step of positioning a distal portion of an ablation instrument in proximity to one or more pulmonary veins. The instrument has a hollow housing and an independently axially positionable energy emitter within the distal portion The energy emitter is configured and the distal portion is shaped such that a distance a beam of ablative energy travels from the energy emitter to the portion of the distal portion in contact with target tissue changes based on the energy emitter&#39;s location along the length of the instrument while the distal portion maintains its shape The energy emitter is a light emitting element and a beam-forming optical waveguide that receives light from the light emitting element. The waveguide projects onto the distal portion a hollow cone of radiation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/357,156, filed Feb. 3, 2003, now U.S. Pat. No. 8,025,661 issued Sep.27, 2011, which is a continuation-in-part of U.S. patent applicationSer. No. 09/924,394, filed on Aug. 7, 2001, now U.S. Pat. No. 6,579,285issued Jun. 17, 2003, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/390,964, filed Sep. 7, 1999, now U.S. Pat. No.6,270,492 issued Aug. 7, 2001, which is a continuation-in-part of U.S.patent application Ser. No. 08/991,130, filed Dec. 16, 1997, now U.S.Pat. No. 5,947,959 issued Sep. 7, 1999, which is a continuation-in-partof U.S. patent application Ser. No. 08/827,631, filed Apr. 10, 1997, nowU.S. Pat. No. 5,908,415 issued Jun. 1, 1999, which is a continuation ofU.S. patent application Ser. No. 08/303,605, filed Sep. 9, 1994,abandoned.

As noted above, the application is a divisional of U.S. patentapplication Ser. No. 10/357,156, filed Feb. 3, 2003, which is also acontinuation-in-part of U.S. patent application Ser. No. 09/616,275filed Jul. 14, 2000, now U.S. Pat. No. 6,626,900 issued Sep. 30, 2003,which is a continuation-in-part of U.S. patent application Ser. No.09/602,420 filed Jun. 23, 2000, now U.S. Pat. No. 6,572,609 issued June3, 2003, which is a continuation-in-part of U.S. patent application Ser.No. 09/357,355, filed on Jul. 14, 1999, now U.S. Pat. No. 6,423,055issued Jul. 22, 2002. The teachings of all of these prior relatedapplications are hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to ablation instruments for ablation oftissue for the treatment of diseases, and, in particular, topercutaneous instruments employing radiant energy. Methods of ablatingtissue using radiant energy are also disclosed. The instruments can beused, for example, in the treatment of cardiac conditions such ascardiac arrhythmias.

Cardiac arrhythmias, e.g., fibrillation, are irregularities in thenormal beating pattern of the heart and can originate in either theatria or the ventricles. For example, atrial fibrillation is a form ofarrhythmia characterized by rapid randomized contractions of atrialmyocardium, causing an irregular, often rapid ventricular rate. Theregular pumping function of the atria is replaced by a disorganized,ineffective quivering as a result of chaotic conduction of electricalsignals through the upper chambers of the heart. Atrial fibrillation isoften associated with other forms of cardiovascular disease, includingcongestive heart failure, rheumatic heart disease, coronary arterydisease, left ventricular hypertrophy, cardiomyopathy or hypertension.

Various techniques have been proposed for the treatment of arrhythmia.Although these procedures were originally performed with a scalpel,various other techniques have also been developed to form lesions.Collectively, these treatments are referred to as “ablation.” Innon-surgical ablations, the tissue is treated, generally with heat orcold, to cause coagulation and/or tissue necrosis (i.e., celldestruction). In each of these techniques, cardiac muscle cells arereplaced with scar tissue which cannot conduct normal electricalactivity within the heart.

For example, the pulmonary vein has been identified as one of theorigins of errant electrical signals responsible for triggering atrialfibrillation. In one known approach, circumferential ablation of tissuewithin the pulmonary veins or at the ostia of such veins has beenpracticed to treat atrial fibrillation. Similarly, ablation of theregion surrounding the pulmonary veins as a group has also beenproposed. By ablating the heart tissue (typically in the form linear orcurved lesions) at selected locations, electrical conductivity from onesegment to another can be blocked and the resulting segments become toosmall to sustain the fibrillatory process on their own.

Several types of ablation devices have recently been proposed forcreating lesions to treat cardiac arrhythmias, including devices whichemploy electrical current (e.g., radio-frequency “RF”) heating orcryogenic cooling. Such ablation devices have been proposed to createelongated lesions that extend through a sufficient thickness of themyocardium to block electrical conduction. Many of the recently proposedablation instruments are percutaneous devices that are designed tocreate such lesions from within the heart. Such devices are positionedin the heart by catheterization of the patient, e.g., by passing theablation instrument into the heart via a blood vessel, such as thefemoral vein.

Devices that rely upon resistive or conductive heat transfer can beprone to serious post-operative complications. In order to quicklyperform an ablation with such “contact” devices, a significant amount ofenergy must be applied directly to the target tissue site. In order toachieve transmural penetration, the surface that is contacted willexperience a greater degree of heating (or freezing). For example, in RFheating of the heart wall, a transmural lesion requires that the tissuetemperature be raised to about 50° C. throughout the thickness of thewall. To achieve this, the temperature at the contact surface willtypically be raised to greater than 100° C. In this temperature regime,there is a substantial risk of tissue destruction (e.g., due to watervaporization micro-explosions or due to carbonization). Charring of thesurface of the heart tissue, in particular, can lead to the creation ofblood clots on the surface and post-operative complications, includingstroke. Even if structural damage is avoided, the extent of the lesion(i.e., the width of the ablated zone) on the surface that has beencontacted will typically be greater than necessary.

Ablation devices that do not require direct contact have also beenproposed, including acoustic and radiant energy. Acoustic energy (e.g.,ultrasound) is poorly transmitted into tissue (unless a coupling fluidis interposed). Laser energy has also been proposed but only in thecontext of devices that focus light into a scalpel-like point or similarhigh intensity spot pattern. When the light energy is delivered in theform of a focused spot, the process is inherently time consuming becauseof the need to expose numerous spots to form a continuous linear orcurved lesion.

In addition, existing instruments for cardiac ablation also suffer froma variety of design limitations. The shape of the heart muscle adds tothe difficulty in accessing cardiac structures, such as the pulmonaryveins on the anterior surface of the heart. Typically, percutaneousdevices are positioned with the assistance of a guide wire, which isfirst advanced into heart. In one common approach, described, forexample, in U.S. Pat. No. 6,012,457 issued to Lesh on Jan. 11, 2000 andin International Application Pub. No. WO 00/67656 assigned to Atrionix,Inc, a guide wire or similar guide device is advanced through the leftatrium of the heart and into a pulmonary vein. A catheter instrumentwith an expandable element is then advanced over the guide and into thepulmonary vein where the expandable element (e.g., a balloon) isinflated. The balloon structure also includes a circumferential ablationelement, e.g., an RF electrode carried on the outer surface of theballoon, which performs the ablation procedure. The balloon must belarge enough and sufficiently rigid to hold the electrode in contactwith the inner surface of the pulmonary vein for the length of theprocedure. Moreover, because the lesion is formed by an ablation elementcarried on the surface of the balloon element, the balloon shapeinherently limits the locations where a lesion can be formed, i.e., thelesion must be formed at least partially within the pulmonary vein.

In another approach described in U.S. Pat. No. 6,235,025 issued toSwartz et al. on May 22, 2001, a guide wire is again used topercutaneously access a pulmonary vein and a catheter is again slid overthe guide to a position within the pulmonary vein. The catheter deviceincludes two spaced-apart balloons, which are inflated in the vein (orin the vein and at its mouth). The space between the two balloons canthen be filled with a conductive fluid to delivery RF energy (or,alternatively, ultrasound) to the vein and thereby induce a conductionblock in the blood vessel by tissue ablation. With the Swartz et al.device, like the Lesh device, the region where tissue ablation can occuris limited by the design. Because two balloons must seal a space that isthen filled with an ablative fluid, the lesion is necessarily formedwithin the pulmonary vein.

Ablation within the pulmonary vein can result in complications.Overtreatment deep within a vein can result in stenosis (closure of thevein itself), necrosis or other structural damage, any of which cannecessitate immediate open chest surgery.

A major limitation in the prior art percutaneous designs is the lack ofsite selectability. Practically speaking, each prior art percutaneousinstrument is inherently limited by its design to forming an ablativelesion at one and only one location. For example, when an expandableballoon carrying an RF heating surface on its surface is deployed at themouth of a vein, the lesion can only be formed at a location defined bythe geometry of the device. It is not possible to form the lesion atanother location because the heating element must contact the targettissue. Similarly the above-described tandem balloon device can onlyform a lesion at a location defined by the space between the balloonsthat is filled with the ablative fluid.

Another major limitation in prior art percutaneous designs is theirinability to accommodate the actual and quite varied geometry of theheart. The inner surface of the atrium is not regular. In particular,the mouths of the pulmonary veins do not exhibit regularity; they oftenbear little resemble to conical or funnel-shaped openings. When theexpandable, contact heating devices of the prior art encounterirregularly-shaped ostia, the result can be an incompletely formed(non-circumferential) lesion.

Accordingly, a percutaneous ablation device that allowed the clinicianto select the location of the ablation site would be highly desirable.An instrument that allows a clinician to choose from a number ofdifferent lesion locations, especially in creating continuous conductionblocks around pulmonary veins, would satisfy a long felt need in theart.

Moreover, the prior art devices typically can not determine whethercontinuous circumferential contact has been achieved before heatingcommences. These devices most often rely on post-ablation electricalmapping to determine whether a circumferential lesion has been formed.If electric conduction is still present, the encircling lesion isincomplete and the procedure must be repeated or abandoned.

Accordingly, there also exists a need for better surgical ablationinstruments that can form lesions with less trauma to the healthy tissueof the heart and greater likelihood of success. A percutaneous systemthat could determine whether contact has been achieved (or blood hasbeen cleared from the target site) and predict success based on suchdeterminations would represent a significant improvement over theexisting designs.

SUMMARY OF THE INVENTION

Ablation methods and instruments are disclosed for creating lesions intissue, especially cardiac tissue for treatment of arrhythmias and thelike. In one aspect of the invention, percutaneous ablation instrumentsin the form of coaxial catheter bodies are disclosed having at least onecentral lumen therein and having one or more balloon structures at thedistal end region of the instrument. The balloon structure and catheterbodies are at least partially transmissive to ablative energy. Theinstruments can further include an energy emitting element, which isindependently positionable within the lumen of the instrument andadapted to project ablative energy through a transmissive region of theballoon to a target tissue site. The energy is delivered without theneed for contact between the energy emitter and the target tissuebecause the methods and devices of the present invention do not relyupon conductive or resistive heating. Because the position of theradiant energy emitter can be varied, the clinician can select thelocation of the desired lesion.

In another aspect of the invention, generally applicable to a wide rangeof cardiac ablation instruments, mechanisms are disclosed fordetermining whether the instrument has been properly seated within theheart, e.g., whether the device is in contact with a pulmonary veinand/or the atrial surface, in order to form a lesion by heating, coolingor projecting energy. This contact-sensing feature can be implemented byan illumination source situated within the instrument and an opticaldetector that monitors the level of reflected light. Measurements of thereflected light (or wavelengths of the reflected light) can thus be usedto determine whether contact has been achieved and whether such contactis continuous over a desired ablation path.

The instruments are especially useful in percutaneous access cardiacsurgery for rapid and efficient creation of curvilinear lesions to serveas conduction blocks. The instruments are designed to create lesions inthe atrial tissue in order to electrically decouple tissue segments onopposite sides of the lesion while presenting low profiles duringpercutaneous access and retraction. The instruments of the presentinvention permit the formation of continuous lesions in the atrial walltissue of the heart, such that the continuous lesion can surround aorgan structure, such as a pulmonary vein, without involving thestructure itself.

In one embodiment a cardiac ablation instrument is disclosed having acatheter body adapted for disposition within a heart. This catheter bodyhas at least one lumen therein and an expandable, energy-transmittingelement which can be deployed at the desired location with or without ananchorage element to contact a cardiac structure and establish atransmission pathway. For example, the expandable element can be aprojection balloon that is expandable to fill the space between theenergy emitter and the target tissue with an energy-transmissive fluidand, thereby, provide a transmission pathway for projected radiantenergy. The instrument further includes a radiant energy deliveryelement movable within the lumen of the catheter body such that it canbe disposed at the desired location and deliver radiant energy through atransmissive region of the instrument to a target tissue site. Theinstrument can further include additional elements, such as fluiddelivery ports, to provide a blood-free transmission pathway from theenergy emitter to the tissue target.

In another embodiment, a cardiac ablation instrument is disclosed havinga catheter body adapted for disposition within a heart and at least oneanchorage element which can be deployed at the desired location tocontact a cardiac structure and secure the device in place. Theinstrument again includes a radiant energy delivery element movablewithin the lumen of the catheter body such that it can be disposed atthe desired location and deliver radiant energy through a transmissiveregion of the instrument to a target tissue site. A projection ballooncan again be employed, alone or together with fluid releasingmechanisms, to provide a blood-free transmission pathway from the energyemitter to the tissue target.

Mechanisms are disclosed for determining whether the ablationinstruments of the present invention have been properly seated withinthe heart to form a lesion. For example, if a projection balloon isemployed to provide a clear transmission pathway from a radiant energyemitter to the target tissue, the mechanisms of the present inventioncan sense whether contact has been achieved between the balloon and thetarget tissue (and/or whether the pathway for projection of radiantenergy has been otherwise cleared of obstructions). In one embodiment,this contact-sensing feature can be implemented by an illumination fibersituated within the instrument and an optical detector fiber (or fiberassembly) that monitors the level of reflected light. Measurements ofthe reflected light (or wavelengths of the reflected light) can thus beused to determine whether contact has been achieved between theprojection balloon and the target tissue, whether blood has been clearedfrom any gaps and whether a clear and continuous transmission pathwayhas been established over a desired ablation path.

In a further aspect of the invention, percutaneous instruments aredisclosed that can achieve rapid and effective photoablation through theuse of tissue-penetrating radiant energy. It has been discovered thatradiant energy, e.g., projected electromagnetic radiation or ultrasound,can create lesions in less time and with less risk of the adverse typesof surface tissue destruction commonly associated with prior artapproaches. Unlike instruments that rely on thermal conduction orresistive heating, controlled penetrating radiant energy can be used tosimultaneously deposit energy throughout the full thickness of a targettissue, such as a heart wall, even when the heart is filled with blood.Radiant energy can also produce better defined and more uniform lesions.

The use of radiant energy, in conjunction with catheter structures thatare substantially transparent to such radiation at the therapeuticwavelengths, is particularly advantageous in affording greater freedomin selecting the location of the lesion, e.g., the site is no longerlimited to the pulmonary vein itself. Because the energy can beprojected onto the tissue, a ring-like lesion can be formed in atrialtissue at a distance from the vein, thereby reducing the potential forstenosis and/or other damage to the vein itself.

It has also been discovered that infrared radiation is particularlyuseful in forming photoablative lesions. In certain preferredembodiments, the instruments emit radiation at a wavelength in a rangefrom about 800 nm to about 1000 nm, and preferably emit at a wavelengthin a range of about 915 nm to about 980 nm. Radiation at a wavelength of915 nm or 980 nm is commonly preferred, in some applications, because ofthe optimal absorption of infrared radiation by cardiac tissue at thesewavelengths.

In another embodiment, focused ultrasound energy can be used to ablatecardiac tissue. In certain preferred embodiments, an ultrasoundtransducer can be employed to transmit frequencies within the range ofabout 5 to about 20 MHz, and preferably in some applications within therange of about 7 MHz to about 10 MHz. In addition, the ultrasonicemitter can include focusing elements to shape the emitted energy intoan annular beam.

However, in certain applications, other forms of radiant energy can alsobe useful including, but not limited to, other wavelengths of light,other frequencies of ultrasound, x-rays, gamma-rays, microwave radiationand hypersound.

In the case of radiant light, the energy delivering element can includea light transmitting optical fiber adapted to receive ablative radiationfrom a radiation source and a light emitting tip at a distal end of thefiber for emitting radiation. The light delivering element can beslidably disposed within an inner lumen of the catheter body and theinstrument can further include a translatory mechanism for disposing thetip of the light delivering element at one or more of a plurality oflocations with the catheter. Moreover, by moving the energy-projectingtip assembly within the catheter, the diameter of the projected ring ofenergy can be readily varied, thereby permitting the clinician controlover the location (and size) of the lesion to be formed.

Optionally, a fluid can be disposable between the radiant energydelivery element and the target region. In one preferred embodiment a“projection balloon” is filled with a radiation-transmissive fluid sothat radiant energy from the energy emitter can be efficiently passedthrough the instrument to the target region. The fluid can also be usedto cool the energy emitter. In certain applications, it can be desirableto use deuterium oxide (so-called “heavy water”) as a balloon-fillingfluid medium because of its loss absorption characteristics vis-à-visinfrared radiation. In other applications, the inflation fluid can bewater or saline.

It can also be desirable to employ an “ablative fluid” outside of theinstrument (e.g., between the balloon and the target region) to ensureefficient transmission of the radiant energy when the instrument isdeployed. An “ablative fluid” in this context is any fluid that canserve as a conductor of the radiant energy. This fluid can be aphysiologically compatible fluid, such as saline, or any other non-toxicaqueous fluid that is substantially transparent to the radiation. In onepreferred embodiment, the fluid is released via one or more exit portsin the housing and flows between the projection balloon and thesurrounding tissue, thereby filling any gaps where the balloon does notcontact the tissue. The fluid can also serve an irrigation function bydisplacing any blood within the path of the radiant energy, which couldotherwise interfere because of the highly absorptive nature of bloodwith respect to radiant light energy.

Similarly, if the radiant energy is acoustic, aqueous coupling fluidscan be used to ensure high transmission of the energy to the tissue (andlikewise displace blood that might interfere with the radiant acousticenergy transfer).

The ablative fluids of the present invention can also include variousother adjuvants, including, for example, photosensitizing agents,pharmacological agents and/or analgesics.

As noted above, contact sensing mechanisms are also disclosed to assistthe clinician in selecting the location of the lesion and in ensuring aselected location will result in the formation of a continuous (e.g.,vein encircling) lesion. In one embodiment the sensor employs aplurality of reflection sensors that indicate whether or not a cleartransmission pathway has been established (e.g., whether the projectionballoon is properly seated and any gaps in contact have been filled byan ablative fluid).

The coaxial catheter instruments disclosed herein are of particular usein percutaneous applications whereby a balloon catheter with an ablativelight or ultrasound projecting assembly can be disposed within apatient's heart. In another aspect of the invention, dual, coaxialballoon structures are disclosed, having both a projection balloon andan anchoring balloon to assist in the proper disposition of theinstrument.

In the dual, coaxial, catheter embodiment, the catheter instrument caninclude at least one expandable anchor balloon disposed about, orincorporated into an inner catheter body designed to slide over aguidewire. This anchor balloon is generally or substantially sealed andserves to position the device within a lumen, such as a pulmonary vein.The anchor balloon structure, when filled with fluid, expands and isengaged in contact with tissue, e.g., the inner surface of a pulmonaryvein.

A second catheter carrying the projection balloon can then be slid overthe first (anchor balloon) catheter body and inflated within the heart,e.g., within the left atrium and adjacent to the pulmonary vein wherethe anchor balloon has already been placed. The expanded projectionballoon thus defines a staging from which to project radiant energy inaccordance with the invention. An energy emitting element can then beintroduced via an inner lumen to project radiant energy, e.g., infraredlight or ultrasound, through the coaxial catheter bodies and theprojection balloon to form a lesion at the target treatment site. Theinstrument can also include an irrigation mechanism for delivery of anablative fluid at the treatment site. In one embodiment, irrigation isprovided by a sheath, partially disposed about the projecting balloon,and provides irrigation at a treatment site (e.g. so that blood can becleared from an ablation site).

Both the anchor and projection balloon structures can be deflated byapplying a vacuum which removes the fluid from the balloons. Once fullydeflated, the coaxial instrument can be removed from the body lumeneither as an ensemble, or as individual elements (starting with theinnermost element). Alternatively, the energy delivery element can beremoved (via an inner lumen balloon structure), followed by theprojection balloon catheter and then the anchor balloon catheter.

The invention can also be used in conjunction with one or more mappingcatheters. For example the guide wire element (and/or the anchorageballoon catheter) can be removed and replaced with a mapping catheterbefore and/or after the lesion is formed to determine whether theablation has been successful in stopping errant electrical signals frompropagating in the atrial wall tissue.

The present invention also provides methods for ablating tissue. Onemethod of ablating tissue comprises positioning a radiant energyemitting element at a distance from a target region of tissue, providinga blood-free transmission pathway between the emitter and the targetregion, and then projecting radiant energy to expose the target regionand induce a lesion.

In one method according to the invention, a guide wire is first insertedinto the femoral vein and advanced through the inferior vena cava, andinto the right atrium, or, if required, it is guided into the leftatrium via an atrial septal puncture. In either event, the guide wire isadvanced until it enters a pulmonary vein. The first catheter body isthen slid over the guide wire until its anchorage element, e.g., theanchor balloon, is likewise advanced into the pulmonary vein. The anchorballoon is then inflated via an inflation fluid to secure the firstcatheter body. Next, a second catheter body is advanced, coaxially, overthe first catheter body, carrying a projection balloon to the treatmentsite. Once the projection balloon is proximate to the target tissueablation site, it can likewise be inflated. In addition, a solution canbe injected through the instrument to force blood and/or body fluidsaway from the treatment site.

The guide wire is then removed and replaced with the radiant energyemitter, which is positioned to deliver radiant energy through theprojection balloon to induce tissue ablation. The methods of the presentinvention can further include a position sensing step to assist theclinician in selecting the location of the lesion and in ensuring aselected location will result in the formation of a continuous (e.g.,vein encircling) lesion. In one embodiment, one or more reflectionsensors are activated to determine whether a clear transmission pathwayhas been established (e.g., whether the projection balloon is properlyseated and any gaps in contact have been filled by an ablative fluid).

Following the ablation procedure, the radiant energy emitter is removedfrom the central lumen of the first catheter body. The anchor ballooncan then be deflated by applying a vacuum that removes the inflationfluid from the balloon. A syringe or other known methods can be used toremove the fluid. In one embodiment, the anchor balloon can be deflatedfirst and removed along with the first (inner) catheter body. The firstcatheter body can then be replaced with a mapping catheter. Once themapping electrode is advanced into the pulmonary vein, the projectionballoon can be likewise deflated and the second catheter body removed,thus leaving only the mapping catheter in place. The mapping cathetercan then be activated to determine whether a conduction block has beenachieved. If the ablation is successful, the mapping catheter can beremoved. If conduction is still present, the procedure can be repeated,for example, by reintroducing the second catheter body, followed byremoval of the mapping catheter, and repositioning the anchor balloonand the radiant energy emitter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich like reference numerals designate like parts throughout thefigures, and wherein:

FIG. 1 is a schematic, cross-sectional view of a coaxial catheterablation instrument according to the invention;

FIG. 2 is a schematic illustration of an initial step in performingablative surgery with radiant energy according to the invention, inwhich a guide wire is introduced into a heart and passed into apulmonary vein;

FIG. 3 is a schematic illustration of another step in performingablative surgery with radiant energy according to the invention, inwhich a first catheter, carrying an anchoring balloon structure, is slidover the guide wire;

FIG. 4 is a schematic illustration of a further step in performingablative surgery according to the invention, in which an anchoringballoon structure is inflated;

FIG. 5 is a schematic illustration of a further step in performingablative surgery according to the invention, in which a second catheter,carrying a projection balloon element, is slid over the first catheterbody;

FIG. 6 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the projectionballoon element of the second catheter is inflated to define aprojection pathway for radiant energy ablation of cardiac tissue;

FIG. 7 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the guide wire isremoved and replaced by a radiant energy emitter located remote from thelesion site but in a position that permits projection of radiant energyonto a target region of the heart;

FIG. 8 is a schematic illustration of a step in performing ablativesurgery according to the invention, in which the radiant energy emitteris positioned to form a lesion at a defined location;

FIG. 9 is a schematic illustration of an alternative step in performingablative surgery according to the invention, in which the radiant energyemitter is positioned to form a lesion at a different defined location;

FIG. 10 is a schematic illustration of a further step in performingablative surgery according to the invention, in which radiant energyemitter is removed and the anchor balloon element of the first catheteris deflated to permit removal of the first catheter body;

FIG. 11 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the first catheteris replaced by a mapping electrode;

FIG. 12 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the projectionballoon is deflated and removed while the mapping electrode remains inplace to verify the formation of an electrical conduction block;

FIG. 13 is a schematic illustration of alternative approach to ablativesurgery with radiant energy according to the invention, in which acatheter carrying an projection balloon structure, is slid over a guidewire without first introducing an anchoring balloon catheter;

FIG. 14 is a schematic illustration of a further step in performingablative surgery with the embodiment illustrated in FIG. 13, in whichthe projection balloon element is inflated to define a projectionpathway for radiant energy ablation of cardiac tissue;

FIG. 15 is a schematic illustration of a further step in performingablative surgery with the embodiment illustrated in FIG. 13, in whichthe guide wire is removed and replaced by a radiant energy emitterlocated remote from the lesion site but in a position that permitsprojection of radiant energy onto a target region of the heart;

FIG. 16 is a schematic illustration of a system according to theinvention in which an asymmetric vein mouth is encountered and furthershowing how the position of the radiant energy emitter can be adjustedto sense contact and select a location; FIG. 16A illustrates how acontinuous, vein-encircling lesion can be formed by twopartially-encircling lesions;

FIG. 17 is a schematic illustration of one embodiment of a radiant lightenergy emitter according to the invention;

FIG. 18 is a schematic illustration of another embodiment of a radiantlight energy emitter according to the invention;

FIG. 19 is a schematic illustration of an alternative embodiment of aradiant energy emitter according to the invention employing ultrasoundenergy;

FIG. 20 is a schematic illustration of an alternative embodiment of aradiant light energy emitter according to the invention employingmicrowave or ionizing radiation;

FIG. 21 is a schematic cross-sectional illustration of one embodiment ofa contact sensor according to the invention;

FIG. 22 is an end view, schematic illustration of the contact sensorelements shown in FIG. 21;

FIG. 23 is a schematic view of a contact heating ablation deviceemploying the contacting sensing apparatus of the present invention;FIG. 23A is a schematic view of a croygenic ablation device employingthe contacting sensing apparatus of the present invention; FIG. 23B is aschematic view of a ultrasound heating ablation device employing thecontacting sensing apparatus of the present invention and

FIG. 24 is a schematic illustration of a mechanism for positioning theradiant energy emitter at a selected location relative to the targettissue region.

DETAIL DESCRIPTION

FIG. 1 provides a schematic, cross-sectional view of a coaxial catheterablation instrument 10 according to the invention, including a first,inner catheter 12 having an elongate body 14 and an anchor balloon 16,inflatable via one or more ports 18. A fluid for inflating the anchorballoon can be delivered through a passageway (not shown) within theelongate body or via one or more of the lumens of the device, asdiscussed in more detail below. The device can further include a second,coaxial, outer catheter 20 having an elongate body 24 and a projectionballoon 26 inflatable via one or more ports 22. The instrument ispreferably designed such that upon anchorage of the anchor balloon 16within the heart (e.g., within a pulmonary vein), the projection ballooncan be inflated such a shoulder portion 50 of the balloon 26 will beurged into close proximity with a target region 52 of cardiac tissue(e.g. an annular region of the atrial heart wall surrounding the ostiumof a pulmonary vein).

The instrument can also include one or more ports 36 (in fluidcommunication with either the first catheter 12 or second catheter 20,or both) for delivering ablative fluid to the target region. Preferably,the ablative fluid is an energy transmissive medium, which helps deliverlight, radiation or acoustic energy from a radiant energy source to atarget tissue region. The ablative fluid also serves to clear blood fromthe vicinity of the instrument and compensate for irregularities in theshape of the heart that might otherwise compromise the seating of theinstrument. The ablative fluid thus provides a clear transmissionpathway external to the balloon.

Within the projection balloon 26 a radiant energy emitter 40 can bedisposed remotely from the target tissue (e.g., within a central lumenof the coaxial catheters 12, 20). In one embodiment, the radiant energysource includes at least one optical fiber 42 coupled to a distal lightprojecting, optical element 43, which cooperate to project ablativelight energy through the instrument to the target site. The catheterbodies, projection balloon and inflation/ablation fluids are allpreferably substantially transparent to the radiant energy at theselected wavelength to provide a low-loss transmission pathway from theprojection element 44 to the target.

FIG. 2 is a schematic illustration of an initial step in performingablative surgery with radiant energy according to the invention, inwhich a guide wire 6 is introduced into a heart 2 and passed into apulmonary vein 4. FIG. 3 illustrates the next step in performingablative surgery according to the invention, in which a first catheter12, carrying an anchoring balloon structure 16, is slid over the guidewire 6. This first catheter 12 can further include at least one internalfluid passageway (not shown) for inflation of the balloon 12, which issealed to the body of the catheter 14 by distal seal 15 and proximalseal 17, such that the introduction of an inflation fluid into theballoon 16 can inflate the balloon as shown in FIG. 4. For furtherdetails on anchoring balloon structures, see commonly owned, U.S. patentapplication Ser. No. 09/616,303 filed Jul. 14, 2000 entitled “CatheterAnchoring Balloon Structure with Irrigation,” the disclosures of whichare hereby incorporated by reference.

FIG. 5 is a schematic illustration of a further step in performingablative surgery according to the invention, in which a second catheter20, likewise having a elongated body 24 and carrying a projectionballoon element 26, is slid over the first catheter body 14. This secondcatheter 20 also includes at least one internal fluid passageway (notshown) for inflation of the balloon 26, which is sealed to the body 24of the catheter 20 by distal seal 21 and proximal seal 22, such that theintroduction of an inflation fluid into the balloon 26 can inflate theballoon as shown in FIG. 6.

Thus, FIG. 6 illustrates how which the projection balloon 26 of thesecond catheter 20 can be deployed and inflated to define a projectionpathway for radiant energy ablation of cardiac tissue. Second catheterbody 24 has an inner lumen 27 sized to pass over the inner catheter body14. Once it is positioned in the heart, the projection balloon of thesecond catheter is then inflated. The expanded projection balloondefines a staging through which radiant energy can be projected inaccordance with the invention. In one preferred embodiment, theprojection balloon is filled with a radiation-transmissive fluid so thatradiant energy from an energy emitter can be efficiently pass throughthe instrument to a target region of cardiac tissue.

The projection balloons described herein can be preshaped to form aparabolic like shape. This can be accomplished, for example, by shapingand melting a TEFLON® film in a preshaped mold to effect the desiredform. The projection balloons and sheaths of the present invention canbe made, for example, of thin wall polyethylene teraphthalate (PET) witha thickness of the membranes of about 5-50 micrometers.

It should be noted that it is not necessary (and in some cases, notdesirable) for the projection balloon 26 to contact the target tissue inorder to ensure radiant energy transmission. One purpose of theprojection balloon is simply to clear a volume of blood away from thepath of the energy emitter. With reference again to FIG. 1, an ablativefluid 29 can be employed outside of the instrument (e.g., between theballoon 26 and the target region 52) to ensure efficient transmission ofthe radiant energy when the instrument is deployed. The ablative fluidin this context is any fluid that can serve as a conductor of theradiant energy. This ablative fluid can be a physiologically compatiblefluid, such as saline, or any other non-toxic aqueous fluid that issubstantially transparent to the radiation. As shown in FIG. 1, thefluid 29 can be released via one or more exit ports 36 in the firstcatheter body 14 (and/or second catheter body 24) to flow between theprojection balloon 26 and the surrounding tissue, thereby filling anygaps where the balloon 26 does not contact the tissue. The fluid 29 canalso serve an irrigation function by displacing any blood within thepath of the radiant energy, which could otherwise interfere with theradiant light energy transmission to the target region 52.

For alternative designs for delivery of ablative and/or irrigationfluids, see commonly-owned, U.S. patent application Ser. No. 09/660,601,filed Sep. 13, 2000 entitled “Balloon Catheter with Irrigation Sheath,”the disclosures of which are hereby incorporated by reference. Forexample, in one embodiment described in patent application Ser. No.09/660,601, the projection balloon can be partially surrounded by asheath that contains pores for releasing fluid near or at the targetablation site. One of ordinary skill in the art will readily appreciatethat such pores can vary in shape and/or size. A person having ordinaryskill in the art will readily appreciate that the size, quantity, andplacement of the fluid ports of various designs can be varied to providea desired amount of fluid to the treatment site.

FIG. 7 is a schematic illustration of a further step in performingablative surgery according to the invention, in which the guide wire isremoved and replaced by a energy emitter 40 located remote from thedesired lesion site 52 but in a position that permits projection ofradiant energy onto a target region of the heart. The energy emitter canbe introduced into the instrument via the lumen 13 of the innercatheter. In the illustrated embodiment, the energy emitter 40 is aradiant energy emitter and includes at least one optical fiber 42coupled to a distal light projecting, optical element 43, whichcooperate to project ablative light energy through the instrument to thetarget site. In one preferred embodiment, optical element is a lenselement capable of projecting an annular (ring-shaped) beam ofradiation, as described in more detail in commonly owned U.S. Pat. No.6,423,055 issued Jul. 22, 2002, herein incorporated by reference.

FIGS. 8 and 9, taken together, illustrate an advantageous feature of thepresent invention, namely, the ability to select the location a lesionindependent of the instrument design. Because the radiant energy emitterdoes not require contact with a target tissue region and is, in fact,decoupled from the rest of the instrument, the present invention permitsthe clinician to select a desired target region by simply moving theemitter (e.g., within the lumen 14 of the first catheter 12). As shownin FIG. 8, the radiant energy emitter can be positioned to form a widecircumferential lesion (when the shape of the pulmonary vein ostiumwarrants such a lesion) by positioning the radiant energy emitter at therear of the projection balloon—at a distance from the target tissue.Alternatively, a smaller diameter lesion can be formed by positioningthe radiant energy emitter closer to the front of the project balloon,as shown in FIG. 9. Such a lesion can be preferably when the geometer ofthe vein ostium presents a more gradual change in diameter, as shown. Itshould be appreciated that it may be desirable to change the intensityof the emitted radiation depending upon the distance it must beprojected; thus a more intense radiant energy beam may be desirable inthe scheme illustrated in FIG. 8 versus that shown in FIG. 9. The energyemitter 40 and catheter body 24 can each include one or more markers(shown schematically as elements 33 and 35 respectively) to aid indetermining the location or tracking movements of the elements. Markers33 and 35, for example, can be radioopaque lines that can visualizedfluoroscopically. Various other marker mechanisms, such as magnetic,capacitive or optical markers, can also be used.

FIG. 10 is a schematic illustration of a further step in performingablative surgery according to the invention, in which radiant energyemitter 40 (shown in FIGS. 7-9) has been removed and the anchor balloonelement 16 of the first catheter 12 is deflated to permit removal of thefirst catheter body 14.

In FIG. 11, the first catheter is replaced by a mapping electrodecatheter 88 via, for example, the central lumen of the second catheter20. However, it should be appreciated that more than one lumen can beused to provide separate pathways for these instruments. Once themapping electrode is positioned within a pulmonary vein, an electricalpulse can be applied to determine whether the lesion formed by theradiant energy emitter (as described above) is sufficient to serve as aconduction block.

FIG. 12 is a schematic illustration of a final step in which theprojection balloon is deflated and removed while the mapping electroderemains in place to verify the formation of an electrical conductionblock. Various techniques for conducting such tests are known by thoseskilled in the art. In one simple approach, a voltage pulse is appliedby a coronary sinus catheter. The mapping catheter's electrode istouched to the inner wall of the pulmonary vein. If no signal (or asubstantially attenuated signal) is detected, a conduction block canthereby be confirmed. It should also be appreciated that the mappingelectrode can in some instances be used even before the projectionand/or anchor balloons are removed.

FIG. 13 is a schematic illustration of an alternative method ofperforming ablative surgery with radiant energy according to theinvention without the need for an anchoring balloon. As shown in FIG.13, a guide wire 6 can again be introduced into a heart and passed intoa pulmonary vein 4. A catheter 20, carrying projection balloon structure26, is slid over the guide wire 6. This catheter 20 can further includeat least one internal fluid passageway (not shown) for inflation of theballoon 26, which is sealed to the body of the catheter 20 by distalseal 21 and proximal seal 22, such that the introduction of an inflationfluid into the balloon 26 can inflate the balloon.

FIG. 14 illustrates how the projection balloon 26 can then be inflatedto define a projection pathway for radiant energy ablation of cardiactissue. The expanded projection balloon defines a staging through whichradiant energy can be projected in accordance with the invention. In onepreferred embodiment, the projection balloon is filled with aradiation-transmissive fluid so that radiant energy from an energyemitter can be efficiently pass through the instrument to a targetregion of cardiac tissue.

The projection balloons described herein can be preshaped to formvarious shapes (e.g., to assist in seating the instrument at the mouthof a pulmonary vein or at other anatomically defined regions of theheart). As noted above, this can be accomplished, for example, byshaping and melting a TEFLON® film in a preshaped mold to effect thedesired form. Again, the projection balloons can be made, for example,of thin wall polyethylene teraphthalate (PET) with a thickness of themembranes of about 5-50 micrometers.

One purpose of the projection balloon is to clear a volume of blood awayfrom the path of the energy emitter. Towards this end, the instrumentcan further include a fluid releasing mechanism in the form of one ormore fluid ports (or a sheath that contains pores for releasing fluid)near or at the target ablation site. Again, the released fluid can serveas an ablative fluid by clearing a transmission pathway for radiantenergy.

FIG. 15 is a schematic illustration of a further step in performingablative surgery with the device of FIGS. 13-14, in which the guide wireis removed and replaced by a radiant energy emitter 40 located remotefrom the desired lesion site 52 but in a position that permitsprojection of radiant energy onto a target region of the heart. In theillustrated embodiment, the radiant energy emitter 40 includes at leastone optical fiber 42 coupled to a distal light projecting, opticalelement 43, which cooperate to project ablative light energy through theinstrument to the target site. In one preferred embodiment, opticalelement is again a lens element capable of projecting an annular(ring-shaped) beam of radiation, as described in more detail in commonlyowned U.S. Pat. No. 6,423,055 issued Jul. 22, 2002, herein incorporatedby reference. Alternatively, the radiant energy emitter can be anultrasound or microwave energy source, as described in more detail below(in connection with FIGS. 19-20).

FIG. 16 further illustrates the unique utility of themulti-positionable, radiant energy ablation devices of the presentinvention in treating the complex cardiac geometries that are oftenencountered. As shown in the figure, the mouths of pulmonary veinstypically do not present simple, funnel-shaped, or regular conicalsurfaces. Instead, one side of the ostium 4B can present a gentlesloping surface, while another side 4A presents a sharper bend. Withprior art, contact-heating, ablation devices, such geometries willresult in incomplete lesions if the heating element (typically aresisting heating band on the surface of an expandable element) can notfully engage the tissue of the vein or ostium. Because the position ofthe heating band of the prior art devices is fixed, when it does notfully contact the target tissue, the result is an arc, or incompletelyformed ring-type, lesion that typically will be insufficient to blockconduction.

FIG. 16 illustrates how the slidably positionable energy emitters of thepresent invention can be used to avoid this problem. Three potentialpositions of the emitter 40 are shown in the figure (labeled as “A”, “B”and “C”). As shown, positions A and C may not result in optimal lesionsbecause of gaps between the balloon and the target tissue. Position B,on the other hand, is preferably because circumferential contact hasbeen achieved. Thus, the independent positioning of the energy sourcerelative to the balloon allows the clinician to “dial” an appropriatelyring size to meet the encountered geometry. (Although three discretelocations are shown in FIG. 16, it should be clear that emitter can bepositioned in many more positions and that the location can be varied ineither discrete intervals or continuously, if so desired.)

Moreover, in some instances the geometries of the pulmonary vein (or theorientation of the projection balloon relative to the ostium) may besuch that no single annular lesion can form a continuous conductionblock. Again, the present invention provides a mechanism for addressingthis problem by adjustment of the location of the energy emitter to formtwo or more partially circumferential lesions. As shown in FIG. 16A, thedevices of the present invention can form a first lesion 94 and a secondlesion 96, each in the form of an arc or partial ring. Because eachlesion has a thickness (dependent largely by the amount of energydeposited into the tissue) the two lesions can axially combine, asshown, to form a continuous encircling or circumscribing lesion thatblocks conduction.

FIG. 17 is a schematic illustration of one embodiment of a radiantenergy emitter 40A according to the invention. In one preferredembodiment, the radiant energy is electromagnetic radiation, e.g.,coherent or laser light, and the energy emitter 40A projects an hollowcone of radiation that forms an annular exposure pattern uponimpingement with a target surface. For example, as shown in FIG. 1,radiant energy emitter 40A can include an optical fiber 42 incommunication with an annulus-forming optical waveguide 44 having aconcave interior boundary or surface 45. The waveguide 44 passes anannular beam of light to a graded intensity (GRIN) lens 46, which servesto collimate the beam, keeping the beam width the same, over theprojected distance. The beam that exits from the distal window 48 ofenergy emitter 40A will expand (in diameter) over distance, but theenergy will remain largely confined to a narrow annular band. Generally,the angle of projection from the central axis of the optical fiber 42 orwaveguide 44 will be between about 20 and 45 degrees.

The diameter of the annular beam of light will be dependent upon thedistance from the point of projection to point of capture by a surface,e.g., a tissue site, e.g., an interstitial cavity or lumen. Typically,when the purpose of the radiant energy projection is to form atransmural cardiac lesion, e.g., around a pulmonary vein, the diameterof the annular beam will be between about 10 mm and about 33 mm,preferably greater than 10 mm, greater than 15 mm, greater than 20 mm,and most preferably, greater than or equal to 23 mm. Typically, angle ofprojected annular light is between about 20 and about 45 degrees,preferably between about 17 and about 30 degrees, most preferablybetween about 16 and about 25 degrees.

Preferred energy sources for use with the percutaneous ablationinstruments of the present invention include laser light in the rangebetween about 200 nanometers and 2.5 micrometers. In particular,wavelengths that correspond to, or are near, water absorption peaks areoften preferred. Such wavelengths include those between about 805 nm andabout 1060 nm, preferably between about 900 nm and 1000 nm, mostpreferably, between about 915 nm and 980 nm. In a preferred embodiment,wavelengths around 915 nm or around 980 nm are used during endocardialprocedures. Suitable lasers include excimer lasers, gas lasers, solidstate lasers and laser diodes. One preferred AlGaAs diode array,manufactured by Spectra Physics, Tucson, Ariz., produces a wavelength of980 nm.

The optical waveguides, as described in above, can be made frommaterials known in the art such as quartz, fused silica or polymers suchas acrylics. Suitable examples of acrylics include acrylates,polyacrylic acid (PAA) and methacrylates, polymethacrylic acid (PMA).Representative examples of polyacrylic esters include polymethylacrylate(PMA), polyethylacrylate and polypropylacrylate. Representative examplesof polymethacrylic esters include polymethylmethacrylate (PMMA),polyethylmethacrylate and polypropylmethacrylate. In one preferredembodiment, the waveguide 44 is formed of quartz and fused to the endface of fiber 42.

Internal shaping of the waveguide can be accomplished by removing aportion of material from a unitary body, e.g., a cylinder or rod.Methods known in the art can be utilized to modify waveguide to havetapered inner walls, e.g., by grinding, milling, ablating, etc. In oneapproach, a hollow polymeric cylinder, e.g., a tube, is heated so thatthe proximal end collapses and fuses together, forming an integralproximal portion which tapers to the distal end of the waveguide. Inanother approach, the conical surface 45 can be formed in a solid quartzcylinder or rod by drilling with a tapered bore.

Waveguide 44 can be optical coupled to optical fiber 42 by variousmethods known in the art. These methods include for example, gluing, orfusing with a torch or carbon dioxide laser . In one embodiment (shownin FIG. 19), waveguide 44, optical fiber 42 and, optionally, a gradientindex lens (GRIN) 46 are in communication and are held in position byheat shrinking a polymeric jacket material 49, such as polyethyleneterephthalate (PET) about the optical apparatus.

FIG. 18 is a schematic illustration of another embodiment of a radiantenergy emitter 40B according to the invention in which optical fiber 42is coupled to a light diffuser 41 having light scattering particles 47to produce a sidewise cylindrical exposure pattern of ablativeradiation. This embodiment can be useful, for example, in creating alesion within a pulmonary vein. With reference again to FIG. 1, itshould be clear that the radiant energy emitter of the design shown inFIG. 14 can be advanced to front of the projection balloon to permitdiffuse exposure of a pulmonary vein ostium if a lesion is desired inthat location. For further details on the construction of lightdiffusing elements, see U.S. Pat. No. 5,908,415 issued to Sinofsky onJun. 1, 1999, herein incorporated by reference.

FIG. 19 illustrates an alternative embodiment of a radiant energyemitter 40C in which an ultrasound transducer 60, comprising individualshaped transducer elements or lenses 62 which direct the ultrasoundenergy into a cone of energy that can likewise form an annular exposurepattern upon impingement with a target surface. The emitter 40C issupported by a sheath 66 or similar elongate body, enclosing electricalleads, and thereby permitting the clinician to advance the emitterthrough an inner lumen of the instrument to a desired position forultrasound emission.

Yet another embodiment of a radiant energy emitter 40D is illustrated inFIG. 20 where microwave energy is similarly focused into an annularexposure beam. As shown in FIG. 20, the radiant energy emitter caninclude a coaxial transmission line 74 (or similar electrical signalleads) and a helical coil antenna 73. Radiation reflectors 72A and 72Bcooperated to shield and direct the radiation into a cone. In otherembodiments, a radioisotope or other source of ionizing radiation can beused in lieu of the microwave antenna 73, again with appropriateradiation shielding elements 72A and 72B to project a beam of ionizingradiation.

FIGS. 21 and 22 illustrate one embodiment of a contact sensor accordingto the invention incorporated into a radiant emitter assembly. Theassembly can includes an outer, radiant energy transparent body 70 thatencases the assembly and facilitates its slidable positioning within aninner lumen of catheter body 14. The assembly further includes an energyemitter 40 (e.g., like those described above in connection with FIGS.17-20) which can also act as the sensing fiber. In the illustratedembodiment, four illumination fibers 76A-76D are shown. If the ablativeapparatus of the invention is properly positioned within the heart,light transmitted via such fibers will strike the target region, bereflected back, and detected by the energy emitter (or other sensingelement). The use of four illumination fibers allows simultaneous orsequential sensing of contact in four “quadrants.” (It should be clearthat the invention can be practiced with various numbers of illuminatingand/or sensing elements, and with or without use of the energy emitteras an element in the contact sensing module. Moreover, ultrasoundemitters and detectors can also be used in the same manner in lieu ofthe light reflecting mechanisms to determine contact. In any event, theoutput signals of the sensors can be electronically processed andincorporated into a display.)

The sensors of FIGS. 21-22 provide the ability to position thepercutaneous ablation instruments of the present invention at atreatment site such that proper location of the energy emitter vis-à-visthe target tissue (as well a satisfactory degree of contact between theprojection balloon and the tissue) is achieved. This ability is based onreflectance measurements of light scattered or absorbed by blood, bodyfluids and tissue. For example, white light projected from sensingfibers 76 toward tissue has several components including red and greenlight. Red light has a wavelength range of about 600 to about 700nanometers (nm) and green light has a wavelength range of about 500 toabout 600 nm. When the projected light encounters blood or body fluids,most if not all green light is absorbed and hence very little green orblue light will be reflected back toward the optical assembly whichincludes a reflected light collector. As the apparatus is positionedsuch that blood and body fluids are removed from the treatment fieldcleared by an inflated balloon member, the reflectance of green and bluelight increases as biological tissue tends to reflect more green light.As a consequence, the amount of reflected green or blue light determineswhether there is blood between the apparatus and the tissue or not.

For example, as the instrument is positioned in a heart chamber, thegreen-blue reflectance signal should remain nearly at zero until theprojection balloon is inflated and positioned proximal to the surface ofthe heart tissue. When the inflated balloon member contacts the hearttissue (or is close enough that the balloon and ablative fluid releasedby the instrument form a clear transmission pathway), green light isreflected back into the optical assembly and the collector. In oneembodiment, only green light is projected toward the tissue surface. Inanother embodiment, red and green light are both projected toward thetissue surface. The red and green light can be transmittedsimultaneously or separately. The use of both red and green lightprovides the advantage that there is no requirement that the operatorneeds to know how much light must be transmitted into the balloon towardthe tissue surface to insure that a reflectance signal is returned. Theratio of the two different wavelengths can be measured. For example, theinstrument can measure reflectance of both green light and red light.When the intensity of the light is sufficient, reflected red light isdetected throughout the positioning process. Prior to contact of theinstrument, and more specifically the inflated balloon, with the tissuethe ratio of red light to green light would be high. Once a transmissionpathway is established, the ratio drops since more light is reflectedfrom the tissue without any intervening blood to absorb the green light.

The reflected light is transmitted back through a collector, such as anoptical fiber to a spectrophotometer. The spectrophotometer (OceanOptics Spectrometer, Dunedin, Fla., model S-2000) produces a spectrumfor each reflected pulse of reflected light. Commercially availablesoftware (LabView Software, Austin, Tex.) can isolate values forspecific colors and perform ratio analyses.

In any event, the use of multiple optical fiber illumination fiberspositioned about the lumen of the catheter, permit the operator todetermine the plane in which the catheter and balloon should be adjustedto minimize blood between the optical assembly and the treatment site.

One suitable optical fiber/collector is described in U.S. Pat. No.6,071,302, issued to Edward Sinofsky on Jun. 6, 2000, the contents ofwhich are incorporated herein by reference.

Once the operator is satisfied with the positioning of the instrument,radiant energy can then be projected to the target tissue region. If theradiant energy is electromagnetic radiation, e.g., laser radiation, itcan be emitted onto the tissue site via a separate optical fiber or,alternatively, through the same optical fiber used to transmitting thewhite, green or red light. The laser light can be pulsed intermittentlyin synchronous fashion with the positioning/reflecting light to ensurethat the pathway remains clear throughout the procedure.

It should be clear that the contact sensing aspects of the presentinvention are not limited to radiant energy ablation devices but canalso be useful in placement of contact heating or cooling ablationinstruments as well. For example, in FIG. 23, a contact-heating device54 having an expandable element 56 and a contact heating element 58 isshown disposed in a pulmonary vein. The contact heating element can be aline or grid of electrically conductive material printed on the surfaceof the expandable element. In one embodiment, the expandable element canbe substantially opaque to certain wavelengths (e.g., visible light)except for a transparent band 59, on which the contact heating elementis situated. The heating wires should also be sufficiently transparent(or cover a substantially small area of the band) so as to not interferewith reflection signal collection. The device 54 can further include asensor 76 disposed within a central lumen of the device having anilluminating fiber and a plurality of collecting fibers. The sensor 76can be coupled to an optical detector and analyzer 53 that is locatedexternal to the device and can be used to measure light received by thesensor and determine whether contact with the target tissue has beenachieved, as will be discussed in more detail below.

The contact sensor can operate in substantially same fashion asdescribed above. For example, when the ablation device 54 of FIG. 23 ispositioned in a pulmonary vein, and illuminated with light from within,a green-blue reflectance signal should remain nearly at zero until theexpandable element 56 is inflated and positioned proximal to the surfaceof the heart tissue. When the portion of inflated expandable element 56that carries the ablation band 58 contacts the heart tissue, green lightis reflected back into the optical assembly and the collector. In oneembodiment, only green light is projected toward the tissue surface. Inanother embodiment, red and green light are both projected toward thetissue surface. The red and green light can be transmittedsimultaneously or separately. Again, the use of both red and green lightprovides the advantage that there is no requirement that the operatorneeds to know how much light must be transmitted into the balloon towardthe tissue surface to insure that a reflectance signal is returned. Theratio of the two different wavelengths can be measured by the opticaldetector and analyzer 53. For example, the instrument can measurereflectance of both green light and red light. When the intensity of thelight is sufficient, reflected red light is detected throughout thepositioning process. Prior to contact of the instrument, and morespecifically the contact-heating ablation band, with the tissue, theratio of red light to green light would be high. Once contact isestablished, the ratio drops since more light is reflected from thetissue without any intervening blood to absorb the green light, andenergy can be delivered to the target tissue from, for example, aradio-frequency electric current source 55.

In FIG. 23A, another embodiment of a contact sensing catheter is shownin the form of a cryogenic ablation catheter 110 having a catheter body112 and internal conduits 114 for circulation of a cryogenic fluid froma cryogenic fluid source 115. The catheter body includes conductiveregions 116 where the cold temperature can be applied to tissue. Thesensors 76 of the present invention can be disposed in proximity to theconductive regions, as shown and used to determine whether tissuecontact has been made. For example, and similar to as discussed abovewith respect to FIG. 23, the sensors 76 can be coupled to an opticalanalyzer 53.

In FIG. 23B yet another application for the contact sensors is shown inconnection with an ultrasound, contact-heating balloon catheter 120,having a balloon 122 (similar to that discussed above in connection withFIG. 23) for contacting a pulmonary vein and having a band 123 forapplying heat to tissue. The ultrasound ablation instrument 120 furtherincludes transducers 124 driven by actuator 125 to heat the ablativeband 123. Again, the sensors 76 of the present invention can be disposedin proximity to the ablation band 123, as shown, and used to determinewhether tissue contact has been made. For example, and similar to asdiscussed above with respect to FIG. 23, the sensors 76 can be coupledto an optical analyzer 53.

In FIG. 24, a translatory mechanism 80 is shown for controlled movementof a radiant energy emitter within the instruments of the presentinvention. The exemplary positioner 80 is incorporated into a handle 84in the proximal region of the instrument, where the elongate body 82 ofthe radiant energy emitter 40 engages a thumb wheel 86 to controladvancement and retraction of the emitter. It should be clear thatvarious alternative mechanisms of manual or automated nature can besubstituted for the illustrated thumb wheel 86 to position the emitterat a desired location relative to the target tissue region.

In addition, as shown in FIG. 24, the elongate body 82 that supports theradiant energy emitter 40 (e.g., an optical fiber assembly as shown inFIGS. 21-22 or the sheath for the electrical leads as shown inconnection with FIGS. 19-20) can further include position indicia 92 onits surface to assist the clinician in placement of the emitter withinthe projection balloon. The handle can further include a window 90whereby the user can read the indicia (e.g., gradation markers) to gaugehow far the emitter has been advanced into the instrument.

Although described in connection with cardiac ablation procedures, itshould be clear that the instruments of the present invention can beused for a variety of other procedures where treatment with radiantenergy is desirable, including laparoscopic, endoluminal, perivisceral,endoscopic, thoracoscopic, intra-articular and hybrid approaches.

The term “radiant energy” as used herein is intended to encompass energysources that do not rely primarily on conductive or convective heattransfer. Such sources include, but are not limited to, acoustic andelectromagnetic radiation sources and, more specifically, includemicrowave, x-ray, gamma-ray, and radiant light sources. The term “light”as used herein is intended to encompass electromagnetic radiationincluding, but not limited to, visible light, infrared and ultravioletradiation.

The term “continuous” in the context of a lesion is intended to mean alesion that substantial blocks electrical conduction between tissuesegments on opposite sides of the lesion. The terms “circumferential”and/or “curvilinear,” including derivatives thereof, are herein intendedto mean a path or line which forms an outer border or perimeter thateither partially or completely surrounds a region of tissue, or separateone region of tissue from another. Further, a “circumferential” path orelement may include one or more of several shapes, and may be forexample, circular, annular, oblong, ovular, elliptical, or toroidal.

The term “lumen,” including derivatives thereof, in the context ofbiological structures, is herein intended to mean any cavity or lumenwithin the body which is defined at least in part by a tissue wall. Forexample, cardiac chambers, the uterus, the regions of thegastrointestinal tract, the urinary tract, and the arterial or venousvessels are all considered illustrative examples of body spaces withinthe intended meaning.

The term “catheter” as used herein is intended to encompass any hollowinstrument capable of penetrating body tissue or interstitial cavitiesand providing a conduit for selectively injecting a solution or gas,including without limitation, venous and arterial conduits of varioussizes and shapes, bronchoscopes, endoscopes, cystoscopes, culpascopes,colonscopes, trocars, laparoscopes and the like. Catheters of thepresent invention can be constructed with biocompatible materials knownto those skilled in the art such as those listed supra, e.g., silastic,polyethylene, Teflon, polyurethanes, etc. The term “lumen,” includingderivatives thereof, in the context of catheters is intended toencompass any passageway within a catheter instrument (and/or trackotherwise joined to such instrument that can serve as a passageway) forthe passage of other component instruments or fluids or for delivery oftherapeutic agents or for sampling or otherwise detecting a condition ata remote region of the instrument.

It should be understood that the term “balloon” encompasses deformablehollow shapes which can be inflated into various configurationsincluding balloon, circular, tear drop, etc., shapes dependent upon therequirements of the body cavity. Such balloon elements can be elastic orsimply capable of unfolding or unwrapping into an expanded state.

The term “transparent” is well recognized in the art and is intended toinclude those materials which allow transmission of energy through, forexample, the primary balloon member. Preferred transparent materials donot significantly impede (e.g., result in losses of over 20 percent ofenergy transmitted) the energy being transferred from an energy emitterto the tissue or cell site. Suitable transparent materials includefluoropolymers, for example, fluorinated ethylene propylene (FEP),perfluoroalkoxy resin (PFA), polytetrafluoroethylene (PTFE), andethylene-tetrafluoroethylene (ETFE).

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A method of treating atrial fibrillation, comprising: positioning adistal portion of an ablation instrument in proximity to one or morepulmonary veins, the ablation instrument having a hollow housing and anindependently axially positionable energy emitter within the distalportion, the distal portion being transmissive to radiant energy,wherein the energy emitter is configured and the distal portion isshaped such that a distance a beam of ablative energy travels from theenergy emitter to the portion of the distal portion in contact withtarget tissue changes based on the energy emitter's location along thelength of the ablation instrument while the distal portion maintains itsshape, wherein the energy emitter comprises a light emitting element anda beam-forming optical waveguide that receives light from the lightemitting element, wherein the wavequide is located at a distal end ofthe light emitting element and is configured so as to project onto thedistal portion a hollow cone of radiation; axially positioning theenergy emitter at any of a plurality of locations along a length ofdistal portion; activating the energy emitter to transmit energy to thewaveguide located at the distal end of the light emitting element;wherein the waveguide causes the transmitted energy to be confined to anannular band of light energy that is focused on the target tissueregion; and conveying the annular band of light energy through thedistal portion of the housing to form an annular lesion in proximity tothe one or more pulmonary veins.
 2. The method of claim 1 wherein themethod further comprises inflating a projection balloon to clear bloodfrom a transmission pathway between the energy emitter and a targetregion of cardiac tissue.
 3. The method of claim 2 wherein the methodfurther comprises determining whether a clear transmission path existsbetween the energy emitter and the target region based on reflectancemeasurements by an optical sensor disposed within the ablationinstrument.
 4. The method of claim 3 wherein the method furthercomprises measuring at least two different wavelengths of reflectedlight collected by the optical sensor to determine whether a projectionpath has been established.
 5. The method of claim 1 wherein the step ofactivating the energy emitter further comprises activating the lightemitting element to expose the target regions to light energy to inducephotocoagulation of cardiac tissue within the target region.
 6. Themethod of claim 1, wherein the light emitting element generatesphotoablative radiation at a desired wavelength ranging from about 800nm to about 1000 nm.
 7. The method of claim 1, wherein the lightemitting element generates photoablative radiation at a desiredwavelength ranging from about 915 nm to about 980 nm.
 8. The method ofclaim 1, wherein the step of axially positioning includes the step ofadjusting the position of the energy emitter until the energy emitterachieves a position where energy transmitted therefrom will contact asection of the distal portion that is in full circumferential contactwith the target tissue region.
 9. A method of treating atrialfibrillation, comprising: selecting a target tissue region proximate toone or more pulmonary veins; providing an ablation instrument thatincludes a catheter and a projection balloon coupled to the catheter,the ablation instrument having an independently axially positionableenergy emitter within the projection balloon, the projection balloonbeing transmissive to radiant energy, the energy emitter being centrallylocated within an inner catheter that passes through the balloon;positioning the projection balloon of the ablation instrument inproximity to the one or more pulmonary veins such that the projectionballoon is seated against an ostium of the pulmonary vein and a distalend of the balloon is disposed at least partially within the pulmonaryvein and a portion of the ablation instrument is in a heart chamber;determining a location at which the projection balloon is in fullcircumferential contact with the ostium of the pulmonary vein; axiallypositioning the energy emitter, while the projection balloon remainsseated at the location, at a position along a length of the projectionballoon in which the energy transmitted therefrom will contact a sectionof the projection balloon that is in full circumferential contact withthe target tissue region; and activating the energy emitter to transmitenergy through the projection balloon to cause an annular band ofenergy, having a projection angle of between about 20 degrees to about45 degrees, to be focused on the target tissue region to form an annularlesion in proximity to the one or more pulmonary veins.
 10. The methodof claim 9, further including, prior to the step of activating theenergy emitter, the step of determining whether a clear transmissionpath exists between the energy emitter and the target region based onreflectance measurements by an optical sensor disposed within theablation instrument.
 11. The method of claim 9, wherein the step ofdetermining the location at which the projection balloon is in fullcircumferential contact comprises the step of using reflectancemeasurements obtained by an optical sensor to determine if theprojection balloon is in contact with the target tissue region.
 12. Themethod of claim 9, wherein a portion of the projection balloon that isseated against the ostium is free of any support by the catheter thatterminates at a proximal end of the balloon.
 13. The method of claim 9,wherein the step of activating the energy emitter further comprisesactivating a radiation emitting element to expose the target region toat least one form of radiant energy selected from the group consistingof light, ultrasound, microwave, x-ray, gamma-ray and ionizing radiationto induce photocoagulation of cardiac tissue within a target region. 14.The method of claim 9, wherein the projection balloon includes a distalneck portion that terminates in the distal end of the balloon, thedistal neck portion being at least partially disposed within thepulmonary vein while a more proximal portion of the balloon that has agreater diameter when inflated lies outside the vein and at leastpartially in contact with the ostium.